METLEN and Karatzis Group Launch 330MW / 790MWh Battery Energy Storage System in Thessaly, Strengthening Greece’s Green Transition

METLEN and Karatzis Group Launch 330MW / 790MWh Battery Energy Storage System in Thessaly, Strengthening Greece’s Green Transition

(IN BRIEF) METLEN and Karatzis Group have announced a strategic joint venture to develop a large-scale Battery Energy Storage System (BESS) in Thessaly, Greece, with a capacity of 330 MW / 790 MWh. The €170 million project, scheduled for completion in the second quarter of 2026, will be Greece’s largest standalone storage facility and one of the biggest in Europe. METLEN will hold a 49% stake in the joint venture and Karatzis Group 51%. The partnership builds on their existing cooperation in renewable energy, including a 262 MW solar portfolio launched in 2024. METLEN’s M Renewables division will manage construction, operation, and maintenance of the facility, leveraging its extensive international experience in energy storage projects. The initiative, which requires no public funding, underscores both companies’ commitment to energy transition, grid stability, and long-term sustainability.

(PRESS RELEASE) ATHENS/ LONDON, 9-Oct-2025 — /EuropaWire/ — METLEN (RIC: MTLN.L, Bloomberg: MTLN.LN, MTLN.GA, ADR: MYTHY US) has announced a new strategic partnership with the Karatzis Group of Companies to develop, construct, and operate a Battery Energy Storage System (BESS) in Thessaly, Greece, with an installed capacity of 330 MW / 790 MWh. The joint venture will be jointly owned by METLEN (49%) and Karatzis Group (51%) and represents a major step toward advancing Greece’s renewable energy infrastructure and energy resilience.

Once operational, the Thessaly project will be the largest standalone energy storage facility in Greece and among the largest in Europe, highlighting both companies’ leadership in sustainable energy development. The initiative follows the partners’ previous collaboration on a 262 MW solar portfolio launched in August 2024 in the same region, designed to facilitate the integration and absorption of renewable power into Greece’s grid.

The total investment for the project is estimated at €170 million, with completion targeted for the second quarter of 2026. The project will not rely on public grants or tax incentives, demonstrating its commercial viability and strong private-sector backing.

Under the agreement, METLEN — through its renewable energy arm M Renewables — will oversee the construction, operation, and maintenance of the facility. M Renewables brings extensive global expertise in energy storage, with projects spanning five continents. In 2024 alone, the division successfully completed ~0.7 GWh of energy storage projects and is finalizing agreements for an additional 2.2 GWh of third-party developments worldwide.

This new venture reinforces METLEN’s and Karatzis Group’s shared vision for energy innovation and security, advancing Greece’s transition toward a sustainable and resilient energy system. “Through long-term collaborations like this one, METLEN continues to build the next-generation Utility — one that drives energy transformation and supports the decarbonization of regional energy systems,” the company stated.

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SOURCE: Metlen Εnergy & Metals